(338e) Interactions and Toxicity of Next Generation Graphene-Metal Nanohybrids at the Pulmonary Interfaces: Influence of Emerging Physicochemical Properties

Carbon-metallic nanohybrids are emerging next generation nanomaterials with improved properties and multifunctionalities, and are being pursued for different applications including biomedical, electronic, energy, and environmental fields. However, their potential inhalation exposure and toxicity to humans have not been investigated. This becomes important since these emerging nanohybrids have altered and unique physicochemical properties compared to their parent materials. Thus, the question remains: if the conjugation of the two or more component materials will result in antagonistic or synergistic toxicological consequences. To answer this question, we performed cytotoxicity studies on nanohybrids made from depositing iron nanoparticles onto reduced graphene oxide nanosheets (rGO-Fe), and compared with their parent materials. rGO-Fe nanohybrids were synthesized in house and characterized for physicochemical properties using high resolution transmission electron microscopy, x-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. Moreover, their colloidal stability and sedimentation characteristics in the cell-culture media were determined. Human bronchial epithelial cell line (BEAS-2B) was exposed to the nanohybrids and component materials. Interesting enough, the cell viability for rGO-Fe was found to be lower than for Fe nanoparticles, but higher than for GO. While GO in the cells were distributed evenly, Fe and rGO-Fe nanohybrids accumulated near the nucleus. GO was uptaken slower than Fe and rGO-Fe due to GO’s higher colloidal stability. The trends for cell membrane damage (i.e., LDH leakage), extracellular ROS, and intracellular ROS generation were similar to the cell toxicity results i.e., GO>rGO-Fe>Fe. In all cases, a positive dose-response relationship was established. Scanning electron microscopy suggested that the cellular interaction was dominated by the iron nanoparticles where the cellular toxicity was dominated by the GO counterpart. This suggests the complex interplay of the properties of metal and graphitic nanostructures in their hybridized form causes significant alterations of the toxicity towards pulmonary interfaces.